The most common method of launching a satellite into geostationary orbit comprises a first stage, which is a stage of injection into a transfer orbit by a space launcher, followed, after separation of the launcher and the satellite, by a second stage, during which the satellite provides the rest of the necessary propulsion by means of its own propulsion system, to complete arrival in geostationary orbit.
Generally, around two-thirds of the propellants taken on by the satellite for its own propulsion system are consumed during this second stage, which is the launch stage, and only the remaining one-third of the propellants are used for station keeping and the actual mission of the satellite in geostationary orbit.
This method of launching was developed, particularly in the Western world, as until now it offered the best compromise between technology and economics, both for the launchers and the satellites, and in particular procured the best thrust efficiency for the launchers.
On the commercial market for satellite launches, the billing of launches essentially took into account the masses to be launched, until the launchers which were initially developed for military purposes were made available to the commercial market The arrival on the commercial market of such low cost-price launchers called into question this billing approach, by offering launch prices almost independent of the masses to be launched, and by providing the possibility of taking the satellites almost directly into geostationary orbit due to the fact that these new launchers have reignitable stages. In this case, the last stage, or upper stage, of the launcher can place the satellites) directly in an orbit close to the geostationary orbit and then, after separation of the satellites and this stage of the launcher, the latter, if one wishes to comply with international recommendations on space debris, should go into a so-called “graveyard” orbit, for example around 300 kilometres above the geostationary orbit, and be rendered passive so that no space debris is created. For its or their part, the satellite(s) reach the geostationary orbit by means of its or their own propulsion system(s).
However, this direct geostationary orbit injection method poses a number of problems.
In the event of a double or multiple launch, the structure carrying the satellites cannot be jettisoned in the geostationary orbit, which means that this carrying structure must be kept attached to the upper stage of the launcher to then be released at the same time as the launcher into the graveyard orbit. Furthermore, after the separation, in an orbit close to the geostationary orbit, of the satellites) and the upper stage of the launcher, the latter's thruster(s) must be reignited, at least once, for the upper stage of the launcher to reach the graveyard orbit. Moreover, if the upper stage of the launcher encounters a major problem in the orbit close to the geostationary orbit, the launcher upper stage can remain locked in that orbit or even explode and thus create debris dangerous to the geostationary satellites.
In order to avoid these drawbacks, WO 99/14118 proposes a method of launching into geostationary orbit an artificial satellite injected into this orbit by a space launcher, and such that:                the assembly formed by the last stage of the launcher and the satellite to be injected into the geostationary orbit is first sent directly into a circular orbit, known as the graveyard orbit, close to the geostationary orbit but far enough away from it to avoid any interference with space objects in the geostationary orbit,        the satellite is separated from the last stage of the launcher, which remains in the graveyard orbit, and        the satellite reaches the geostationary orbit from the graveyard orbit by means of its own propulsion system.        
Thus, the launcher sends the satellite into the graveyard orbit, in which the upper stage of the launcher jettisons the satellite, which then reaches the geostationary orbit by its own means. As the upper stage of the launcher is directly in the graveyard orbit, it is no longer necessary to reignite its thrusters(s), and all that is required is to render it passive in the graveyard orbit, which is preferably at an altitude several tens to several hundreds of kilometres away from the geostationary orbit, and in particular around 300 kilometres away from the geostationary orbit.
However, this method nevertheless has the drawback of requiring the use of a more powerful launcher than those allowing for launches into geostationary orbit by the more conventional method comprising a first stage of injection of the satellite into a transfer orbit followed by a second stage during which the satellite reaches the geostationary orbit by means of its own propulsion system.
For reasons of security of supply of launchers, the commercial market requires of satellite manufacturers that their satellites be compatible with the main launchers available on the market, not all of which are currently capable of direct launching into geostationary orbit.